1. Field of the Invention
The present invention relates to improvements in composite photography systems of the type in which different scenes are photographed by separate cameras and are combined to synthesize realistic images. More particularly, the present invention relates to improved foreground and background optical systems requiring variable focussing capability and panning while having correlated optical features that permit a scaling of the background scene to that of foreground action while maintaining registration, constant magnification ratios, dual field of view and minimal distortion and aberration. Finally, the present invention includes a unique background optical system that can be incorporated into optical scanning probes such as simulators.
2. Description of the Prior Art
The combining of a foreground scene which typically includes moving objects such as actors with a background scene to produce a composite picture is known in the prior art. The combining of two images is accomplished by a process wherein the portions of the background scene corresponding to the foreground objects are blanked out or masked by a foreground camera. In film cameras, the masking is accomplished by making an opaque matte of the foreground objects and printing the background scene masked by the matte. The foreground objects are then printed on the masked areas of the background to form the composite picture. When the system is used in cinematography, the cameras may be either film or television. Because the masking matte moves or travels from frame to frame, such a system has come to be referred to in the art as a travelling matte system.
A number of problems exist in accomplishing the goal of accurate registration and composite image quality during relative movement of each camera and the objects in the respective scenes. For example, unless registration is maintained, the desired illusion is lost. As can readily be appreciated, the required degree of accuracy in registration depends upon the intended use of the finished composite picture. Thus, the projection magnification required for widescreen picture projection, for example, requires much more accurate registration than a video format.
Only recently, composite image systems, such as travelling matte systems, have provided the capability of synchronized movement of the cameras relative to their respective frames of reference, including their viewed scenes. The system described in the Slater U.S. Pat. No. 3,914,540 and in the Trumbull et al., U.S. Pat. No. 3,902,798, describes a composite image system which has the capability of synchronizing the background camera movements with the foreground camera movements and the x, y, z, yaw and pitch axes so that a cameraman can "dolly," "crab" or "pedestal" as ordered by the director in the foreground camera in these five axes. A relatively precise camera control servo mechanism controlled by a computer, has been developed to maintain appropriate perspective matching during complex camera movements. For a complete description of such a system, reference should be made to these two patents and they are accordingly incorporated herein by reference as if fully set forth at this point. Additional information can be found in "Magicam-Process and Production Techniques" by Joseph Matza, et al. SMPTE Journal, October 1977, Volume 86 page 728.
As explained in the above patents, the objects viewed by the perspective of the two cameras usually differ in scale or relative size. The scene viewed by the background camera typically is a miniaturized set while the scene viewed by the foreground camera typically would be a life-size actor or object. Combining a life-size actor with a miniature background set, according to the travelling matte technique, will cause the fullsize actors to appear to be in a lifelike environment of the miniaturized set. Because the scene viewed by the background camera is miniaturized, the movements of the background camera must be appropriately scaled to the size of the miniature set. As can be appreciated, the economics realized by using a miniature set can reduce the cost of production while also permitting improved visual special effects. It should also be borne in mind that this technique, however, is not limited to a situation where life-size actors are placed into a miniature set. It also finds application in the remote control of cameras generally such as where, for example, the environment of one or both of the cameras controlled is adverse by being dangerous, relatively inaccessible or the like.
Typically, the foreground camera is mounted on a four-wheel dolly which is steered by an operator while the cameraman rides thereon and shoots the scene being filmed. The dolly is driven and steered by means of all four wheels, wherein all four wheels pointed in the same direction at one time to provide a constant heading. It is, therefore, capable of moving along the ground plane or stage floor in a limitless variety of travel paths. The position and perspective in which the foreground camera views its scene must be duplicated with great accuracy and effectiveness in the background camera along the x, y, z, yaw and pitch axes.
The prior art systems that have utilized a dolly-mounted foreground camera have recognized and have attempted to compensate and correct for errors such as gear back lash, low frequency reasonances in the high gain servo system, electronic noise and unevenness in the stage floor.
The primary consideration in the optical areas has been compensation for the off-axis location of the optical lens of the camera relative to the kinematic pivotal point of the camera. This optical compensation was necessary to insure that registration would be maintained during movement of the foreground camera as the optical lens tracked an arc during pan or tilt movement. For example, the teachings of the U.S. Pat. No. 3,914,540 provided an electrical circuit correction to compensate for this optical misalignment of the foreground and background cameras. The prior art has not provided correlated optical systems to permit maintenance of image registration for a full simulation of the optical characteristics of the foreground camera in a scaled down version in the background camera during variable focussing and panning. The focussing problems that existed are a result of the depth of field variances and foreground object movement relative to camera position which provided severe limitations on the use of composite photography. To date, the prior art has been incapable of providing composite image registration during focussing of at least one camera and during panning.
An additional need has existed in the prior art to provide improved optical scanning probes of minimum altitude and dual fields of view for use in simulators. Of general interest is the article "Optical Scanning Probe Technology" by M. Shenker SPIE Vol. 59, pg. 71 (1975) Simulators and Simulation.
The prior art is still seeking to provide composite photography image systems capable of a high magnification for projection of aberration free images, such as in wide screen movies while permitting variable focussing capability and accurate registration of images.